Micro- and nano-particulate systems have been used widely in various biomedical and pharmaceutical applications, such as drug delivery. Depending on the delivery route and disease site, either microspheres (1 μm-1000 μm) or nanospheres (1 nm-1000 nm) provide suitable delivery systems. For example, nanospheres can be designed as short-acting delivery vehicles and used to induce efficient drug accumulation at a target site, for example, to target a tumor in cancerous tissues. Microspheres can be used as depot drug carriers for long-acting delivery. For example, microvesicles may be used for tissue regeneration by releasing growth factors in a polymeric scaffold.
Synthetic materials, such as biodegradable synthetic polymers, have been used to fabricate micro- and nano-particulate delivery systems. Many of these polymers, however, have inherent limitations for tissue engineering and drug delivery applications. For example, organic solvent is usually needed to dissolve these polymers because of their hydrophobic nature, and the organic solvent may be detrimental to the proteins or other active agents to be loaded in/on the particles. Moreover, the degradation products of many of these polymers are acidic, which may cause the denaturation of proteinaceous or other acid-sensitive drugs. Hence, there remains a need for active agents and processes that provide for microspheres and nanospheres with controllable sphere size and shape, and that avoid using organic solvents and other harsh conditions during the fabrication process.